Advanced pulse oximetry sensor

ABSTRACT

A non-invasive, optical-based physiological monitoring system is disclosed. One embodiment includes an emitter configured to emit light. A diffuser is configured to receive and spread the emitted light, and to emit the spread light at a tissue measurement site. The system further includes a concentrator configured to receive the spread light after it has been attenuated by or reflected from the tissue measurement site. The concentrator is also configured to collect and concentrate the received light and to emit the concentrated light to a detector. The detector is configured to detect the concentrated light and to transmit a signal representative of the detected light. A processor is configured to receive the transmitted signal and to determine a physiological parameter, such as, for example, arterial oxygen saturation, in the tissue measurement site.

INCORPORATION BY REFERENCE TO ANY PRIORITY APPLICATIONS

This present application claims priority benefit under 35 U.S.C. §119(e) from U.S. Provisional Application No. 62/188,430, filed Jul. 2,2015, entitled “Advanced Pulse Oximetry Sensor,” which is incorporatedby reference herein. Any and all applications for which a foreign ordomestic priority claim is identified in the Application Data Sheet asfiled with the present application are hereby incorporated by referenceunder 37 CFR 1.57.

FIELD OF THE DISCLOSURE

The present disclosure relates to the field of non-invasiveoptical-based physiological monitoring sensors, and more particularly tosystems, devices and methods for improving the non-invasive measurementaccuracy of oxygen saturation, among other physiological parameters.

BACKGROUND

Spectroscopy is a common technique for measuring the concentration oforganic and some inorganic constituents of a solution. The theoreticalbasis of this technique is the Beer-Lambert law, which states that theconcentration c_(i) of an absorbent in solution can be determined by theintensity of light transmitted through the solution, knowing thepathlength d₈₀, the intensity of the incident light I_(0,λ), and theextinction coefficient ε_(i,λ) at a particular wavelength λ.

In generalized form, the Beer-Lambert law is expressed as:

$\begin{matrix}{I_{\lambda} = {I_{0,\lambda}e^{{- d_{\lambda}} \cdot \mu_{a,\lambda}}}} & (1) \\{\mu_{a,\lambda} = {\sum\limits_{i = 1}^{n}{ɛ_{i,\lambda} \cdot c_{i}}}} & (2)\end{matrix}$where Ξ_(a,λ) is the bulk absorption coefficient and represents theprobability of absorption per unit length. The minimum number ofdiscrete wavelengths that are required to solve equations 1 and 2 is thenumber of significant absorbers that are present in the solution.

A practical application of this technique is pulse oximetry, whichutilizes a noninvasive sensor to measure oxygen saturation and pulserate, among other physiological parameters. Pulse oximetry relies on asensor attached externally to the patient to output signals indicativeof various physiological parameters, such as a patient's bloodconstituents and/or analytes, including for example a percent value forarterial oxygen saturation, among other physiological parameters. Thesensor has an emitter that transmits optical radiation of one or morewavelengths into a tissue site and a detector that responds to theintensity of the optical radiation after absorption by pulsatilearterial blood flowing within the tissue site. Based upon this response,a processor determines the relative concentrations of oxygenatedhemoglobin (HbO₂) and deoxygenated hemoglobin (Hb) in the blood so as toderive oxygen saturation, which can provide early detection ofpotentially hazardous decreases in a patient's oxygen supply.

A pulse oximetry system generally includes a patient monitor, acommunications medium such as a cable, and/or a physiological sensorhaving one or more light emitters and a detector, such as one or morelight-emitting diodes (LEDs) and a photodetector. The sensor is attachedto a tissue site, such as a finger, toe, earlobe, nose, hand, foot, orother site having pulsatile blood flow which can be penetrated by lightfrom the one or more emitters. The detector is responsive to the emittedlight after attenuation or reflection by pulsatile blood flowing in thetissue site. The detector outputs a detector signal to the monitor overthe communication medium. The monitor processes the signal to provide anumerical readout of physiological parameters such as oxygen saturation(SpO2) and/or pulse rate. A pulse oximetry sensor is described in U.S.Pat. No. 6,088,607 entitled Low Noise Optical Probe; pulse oximetrysignal processing is described in U.S. Pat. Nos. 6,650,917 and 6,699,194entitled Signal Processing Apparatus and Signal Processing Apparatus andMethod, respectively; a pulse oximeter monitor is described in U.S. Pat.No. 6,584,336 entitled Universal/Upgrading Pulse Oximeter; all of whichare assigned to Masimo Corporation, Irvine, Calif., and each isincorporated by reference herein in its entirety.

There are many sources of measurement error introduced to pulse oximetrysystems. Some such sources of error include the pulse oximetry system'selectronic components, including emitters and detectors, as well aschemical and structural physiological differences between patients.Another source of measurement error is the effect of multiple scatteringof photons as the photons pass through the patient's tissue (arterialblood) and arrive at the sensor's light detector.

SUMMARY

This disclosure describes embodiments of non-invasive methods, devices,and systems for measuring blood constituents, analytes, and/orsubstances such as, by way of non-limiting example, oxygen,carboxyhemoglobin, methemoglobin, total hemoglobin, glucose, proteins,lipids, a percentage thereof (e.g., saturation), pulse rate, perfusionindex, oxygen content, total hemoglobin, Oxygen Reserve Index™ (ORI™) orfor measuring many other physiologically relevant patientcharacteristics. These characteristics can relate to, for example, pulserate, hydration, trending information and analysis, and the like.

In an embodiment, an optical physiological measurement system includesan emitter configured to emit light of one or more wavelengths. Thesystem also includes a diffuser configured to receive the emitted light,to spread the received light, and to emit the spread light over a largertissue area than would otherwise be penetrated by the emitter directlyemitting light at a tissue measurement site. The tissue measurement sitecan include, such as, for example, a finger, a wrist, or the like. Thesystem further includes a concentrator configured to receive the spreadlight after it has been attenuated by or reflected from the tissuemeasurement site. The concentrator is also configured to collect andconcentrate the received light and to emit the concentrated light to adetector. The detector is configured to detect the concentrated lightand to transmit a signal indicative of the detected light. The systemalso includes a processor configured to receive the transmitted signalindicative of the detected light and to determine, based on an amount ofabsorption, an analyte of interest, such as, for example, arterialoxygen saturation or other parameter, in the tissue measurement site.

In certain embodiments of the present disclosure, the diffuser comprisesglass, ground glass, glass beads, opal glass, or a microlens-based,band-limited, engineered diffuser that can deliver efficient and uniformillumination. In some embodiments the diffuser is further configured todefine a surface area shape by which the emitted spread light isdistributed onto a surface of the tissue measurement site. The definedsurface area shape can include, by way of non-limiting example, a shapethat is substantially rectangular, square, circular, oval, or annular,among others.

According to some embodiments, the optical physiological measurementsystem includes an optical filter having a light-absorbing surface thatfaces the tissue measurement site. The optical filter also has anopening that is configured to allow the spread light, after beingattenuated by the tissue measurement site, to be received by theconcentrator. In an embodiment, the opening has dimensions, wherein thedimensions of the opening are similar to the defined surface area shapeby which the emitted spread light is distributed onto the surface of thetissue measurement site. In an embodiment, the opening has dimensionsthat are larger than the defined surface area shape by which the emittedspread light is distributed onto the surface of the tissue measurementsite. In other embodiments, the dimensions of the opening in the opticalfilter are not the same as the diffuser opening, but the dimensions arelarger than the detector package.

In other embodiments of the present disclosure, the concentratorcomprises glass, ground glass, glass beads, opal glass, or a compoundparabolic concentrator. In some embodiments the concentrator comprises acylindrical structure having a truncated circular conical structure ontop. The truncated section is adjacent the detector. The lightconcentrator is structured to receive the emitted optical radiation,after reflection by the tissue measurement site, and to direct thereflected light to the detector.

In accordance with certain embodiments of the present disclosure, theprocessor is configured to determine an average level of the lightdetected by the detector. The average level of light is used todetermine a physiological parameter in the tissue measurement site.

According to another embodiment, a method to determine a constituent oranalyte in a patient's blood is disclosed. The method includes emitting,from an emitter, light of at least one wavelength; spreading, with adiffuser, the emitted light and emitting the spread light from thediffuser to a tissue measurement site; receiving, by a concentrator, thespread light after the spread light has been attenuated by the tissuemeasurement site; concentrating, by the concentrator, the received lightand emitting the concentrated light from the concentrator to a detector;detecting, with the detector, the emitted concentrated light;transmitting, from the detector, a signal responsive to the detectedlight; receiving, by a processor, the transmitted signal responsive tothe detected light; and processing, by the processor, the receivedsignal responsive to the detected light to determine a physiologicalparameter.

In some embodiments, the method to determine a constituent or analyte ina patient's blood includes filtering, with a light-absorbing detectorfilter, scattered portions of the emitted spread light. According to anembodiment, the light-absorbing detector filter is substantiallyrectangular in shape and has outer dimensions in the range ofapproximately 1-5 cm in width and approximately 2-8 cm in length, andhas an opening through which emitted light may pass, the opening havingdimensions in the range of approximately 0.25-3 cm in width andapproximately 1-7 cm in length. In another embodiment, thelight-absorbing detector filter is substantially square in shape and hasouter dimensions in the range of approximately 0.25-10 cm², and has anopening through which emitted light may pass, the opening havingdimensions in the range of approximately 0.1-8 cm². In yet anotherembodiment, the light-absorbing detector filter is substantiallyrectangular in shape and has outer dimensions of approximately 3 cm inwidth and approximately 6 cm in length, and has an opening through whichemitted light may pass, the opening having dimensions of approximately1.5 cm in width and approximately 4 cm in length.

In still other embodiments of the method to determine a constituent oranalyte in a patient's blood, spreading, with a diffuser, the emittedlight and emitting the spread light from the diffuser to a tissuemeasurement site is performed by at least one of a glass diffuser, aground glass diffuser, a glass bead diffuser, an opal glass diffuser,and an engineered diffuser. In some embodiments the emitted spread lightis emitted with a substantially uniform intensity profile. And in someembodiments, emitting the spread light from the diffuser to the tissuemeasurement site includes spreading the emitted light so as to define asurface area shape by which the emitted spread light is distributed ontoa surface of the tissue measurement site.

According to yet another embodiment, a pulse oximeter is disclosed. Thepulse oximeter includes an emitter configured to emit light at one ormore wavelengths. The pulse oximeter also includes a diffuser configuredto receive the emitted light, to spread the received light, and to emitthe spread light directed at a tissue measurement sight. The pulseoximeter also includes a detector configured to detect the emittedspread light after being attenuated by or reflected from the tissuemeasurement site and to transmit a signal indicative of the detectedlight. The pulse oximeter also includes a processor configured toreceive the transmitted signal and to process the received signal todetermine an average absorbance of a blood constituent or analyte in thetissue measurement site over a larger measurement site area than can beperformed with a point light source or point detector. In someembodiments, the diffuser is further configured to define a surface areashape by which the emitted spread light is distributed onto a surface ofthe tissue measurement site, and the detector is further configured tohave a detection area corresponding to the defined surface area shape bywhich the emitted spread light is distributed onto the surface of thetissue measurement site. According to some embodiments, the detectorcomprises an array of detectors configured to cover the detection area.In still other embodiments, the processor is further configured todetermine an average of the detected light.

For purposes of summarizing, certain aspects, advantages and novelfeatures of the disclosure have been described herein. It is to beunderstood that not necessarily all such advantages can be achieved inaccordance with any particular embodiment of the systems, devices and/ormethods disclosed herein. Thus, the subject matter of the disclosureherein can be embodied or carried out in a manner that achieves oroptimizes one advantage or group of advantages as taught herein withoutnecessarily achieving other advantages as can be taught or suggestedherein.

BRIEF DESCRIPTION OF THE DRAWINGS

Throughout the drawings, reference numbers can be re-used to indicatecorrespondence between referenced elements. The drawings are provided toillustrate embodiments of the disclosure described herein and not tolimit the scope thereof.

FIG. 1 illustrates a conventional approach to two-dimensional pulseoximetry in which the emitter is configured to emit optical radiation asa point optical source.

FIG. 2 illustrates the disclosed three-dimensional approach to pulseoximetry in which the emitted light irradiates a substantially largervolume of tissue as compared to the point source approach described withrespect to FIG. 1.

FIG. 3 illustrates schematically a side view of a three-dimensionalpulse oximetry sensor according to an embodiment of the presentdisclosure.

FIG. 4A is a top view of a portion of a three-dimensional pulse oximetrysensor according to an embodiment of the present disclosure.

FIG. 4B illustrates the top view of a portion of the three-dimensionalpulse oximetry sensor shown in FIG. 4A, with the addition of a tissuemeasurement site in operational position.

FIG. 5 illustrates a top view of a three-dimensional pulse oximetrysensor according to an embodiment of the present disclosure.

FIG. 6 illustrates a conventional two-dimensional approach to reflectivepulse oximetry in which the emitter is configured to emit opticalradiation as a point optical source.

FIG. 7A is a simplified schematic side view illustration of a reflectivethree-dimensional pulse oximetry sensor according to an embodiment ofthe present disclosure.

FIG. 7B is a simplified schematic top view illustration of thethree-dimensional reflective pulse oximetry sensor of FIG. 7A.

FIG. 8 illustrates a block diagram of an example pulse oximetry systemcapable of noninvasively measuring one or more blood analytes in amonitored patient, according to an embodiment of the disclosure.

DETAILED DESCRIPTION

FIG. 1 illustrates schematically a conventional pulse oximetry sensorhaving a two-dimensional (2D) approach to pulse oximetry. Asillustrated, the emitter 104 is configured to emit optical radiation asa point optical source, i.e., an optical radiation source that hasnegligible dimensions such that it may be considered as a point. Thisapproach is referred to herein as “two-dimensional” pulse oximetrybecause it applies a two-dimensional analytical model to thethree-dimensional space of the tissue measurement site 102 of thepatient. Point optical sources feature a defined, freely selectable, andhomogeneous light beam area. Light beams emitted from LED point sourcesoften exhibit a strong focus which can produce a usually sharply-definedand evenly-lit illuminated spot often with high intensity dynamics.Illustratively, when looking at the surface of the tissue measurementsite 102 (or “sample tissue”), which in this example is a finger, asmall point-like surface area of tissue 204 is irradiated by a pointoptical source. In some embodiments, the irradiated circular area of thepoint optical source is in the range between 8 and 150 microns.Illustratively, the emitted point optical source of light enters thetissue measurement site 102 as a point of light. As the light penetratesthe depth of the tissue 102, it does so as a line or vector,representing a two-dimensional construct within a three-dimensionalstructure, namely the patient's tissue 102.

Use of a point optical source is believed to reduce variability in lightpathlength which would lead to more accurate oximetry measurements.However, in practice, photons do not travel in straight paths. Instead,the light particles scatter, bouncing around between various irregularobjects (such as, for example, red blood cells) in the patient's blood.Accordingly, photon pathlengths vary depending on, among other things,their particular journeys through and around the tissue at themeasurement site 102. This phenomenon is referred to as “multiplescattering.” In a study, the effects of multiple scattering wereexamined by comparing the results of photon diffusion analysis withthose obtained using an analysis based on the Beer-Lambert law, whichneglects multiple scattering in the determination of light pathlength.The study found that that the difference between the average lengths ofthe paths traveled by red and infrared photons makes the oximeter'scalibration curve (based on measurements obtained from normal subjects)sensitive to the total attenuation coefficients of the tissue in the twowavelength bands used for pulse oximetry, as well as to absorption bythe pulsating arterial blood.

FIG. 2 illustrates schematically the disclosed systems, devices, andmethods to implement three-dimensional (3D) pulse oximetry in which theemitted light irradiates a larger volume of tissue at the measurementsite 102 as compared to the 2D point optical source approach describedwith respect to FIG. 1. In an embodiment, again looking at the surfaceof the tissue measurement site 102, the irradiated surface area 206 ofthe measurement site 102 is substantially rectangular in shape withdimensions in the range of approximately 0.25-3 cm in width andapproximately 1-6 cm in length. In another embodiment, the irradiatedsurface area 206 of the measurement site 102 is substantiallyrectangular in shape and has dimensions of approximately 1.5 cm in widthand approximately 2 cm in length. In another embodiment, the irradiatedsurface area 206 of the measurement site 102 is substantiallyrectangular in shape and has dimensions of approximately 0.5 cm in widthand approximately 1 cm in length. In another embodiment, the irradiatedsurface area 206 of the measurement site 102 is substantiallyrectangular in shape has dimensions of approximately 1 cm in width andapproximately 1.5 cm in length. In yet another embodiment, theirradiated surface area 206 of the measurement site 102 is substantiallysquare in shape and has dimensions in a range of approximately 0.25-9cm². In certain embodiments, the irradiated surface area 206 of themeasurement site 102 is within a range of approximately 0.5-2 cm inwidth, and approximately 1-4 cm in length. Of course a skilled artisanwill appreciate that many other shapes and dimensions of irradiatedsurface area 206 can be used. Advantageously, by irradiating the tissuemeasurement site 102 with a surface area 206, the presently disclosedsystems, devices, and methods apply a three-dimensional analytical modelto the three-dimensional structure being measured, namely, the patient'ssample tissue 102.

According to the Beer-Lambert law, the amount of light absorbed by asubstance is proportional to the concentration of the light-absorbingsubstance in the irradiated solution (i.e., arterial blood).Advantageously, by irradiating a larger volume of tissue 102, a largersample size of light attenuated (or reflected) by the tissue 102 ismeasured. The larger, 3D sample provides a data set that is morerepresentative of the complete interaction of the emitted light as itpasses through the patient's blood as compared to the 2D point sourceapproach described above with respect to FIG. 1. By taking an average ofthe detected light, as detected over a surface area substantially largerthan a single point, the disclosed pulse oximetry systems, devices, andmethods will yield a more accurate measurement of the emitted lightabsorbed by the tissue, which will lead to a more accurate oxygensaturation measurement.

FIG. 3 illustrates schematically a side view of a pulse oximetry 3Dsensor 300 according to an embodiment of the present disclosure. In theillustrated embodiment, the 3D sensor 300 irradiates the tissuemeasurement site 102 and detects the emitted light, after beingattenuated by the tissue measurement site 102. In other embodiments, forexample, as describe below with respect to FIGS. 7A and 7B, the 3Dsensor 300 can be arranged to detect light that is reflected by thetissue measurement site 102. The 3D sensor 300 includes an emitter 302,a light diffuser 304, a light-absorbing detector filter 306, a lightconcentrator 308, and a detector 310. In some optional embodiments, the3D sensor 300 further includes a reflector 305. The reflector 305 can bea metallic reflector or other type of reflector. Reflector 305 can be acoating, film, layer or other type of reflector. The reflector 305 canserve as a reflector to prevent emitted light from emitting out of a topportion of the light diffuser 304 such that light from the emitter 302is directed in the tissue rather than escaping out of a side or top ofthe light diffuser 304. Additionally, the reflector 305 can preventambient light from entering the diffuser 304 which might ultimatelycause errors within the detected light. The reflector 305 also preventlight piping that might occur if light from the detector 302 is able toescape from the light diffuser 304 and be pipped around a sensorsecurement mechanism to detector 310 without passing through thepatient's tissue 102.

The emitter 302 can serve as the source of optical radiation transmittedtowards the tissue measurement site 102. The emitter 302 can include oneor more sources of optical radiation, such as LEDs, laser diodes,incandescent bulbs with appropriate frequency-selective filters,combinations of the same, or the like. In an embodiment, the emitter 302includes sets of optical sources that are capable of emitting visibleand near-infrared optical radiation. In some embodiments, the emitter302 transmits optical radiation of red and infrared wavelengths, atapproximately 650 nm and approximately 940 nm, respectively. In someembodiments, the emitter 302 includes a single source optical radiation.

The light diffuser 304 receives the optical radiation emitted from theemitter 302 and spreads the optical radiation over an area, such as thearea 206 depicted in FIG. 2. In some embodiments, the light diffuser 304is a beam shaper that can homogenize the input light beam from theemitter 302, shape the output intensity profile of the received light,and define the way (e.g., the shape or pattern) the emitted light isdistributed to the tissue measurement site 102. Examples of materialsthat can be used to realize the light diffuser 304 include, withoutlimitation, a white surface, glass, ground glass, glass beads,polytetrafluoroethylene (also known as Teflon®, opal glass, and greyedglass, to name a few. Additionally, engineered diffusers can be used torealize the diffuser 304 by providing customized light shaping withrespect to intensity and distribution. Such diffusers can, for example,deliver substantially uniform illumination over a specified target area(such as, for example, irradiated surface area 206) in anenergy-efficient manner. Examples of engineered diffusers can includemolded plastics with specific shapes, patterns or textures designed todiffuse the emitter light across the entirety of the patient's tissuesurface.

Advantageously, the diffuser 304 can receive emitted light in the formof a point optical source and spread the light to fit a desired surfacearea on a plane defined by the surface of the tissue measurement site102. In an embodiment, the diffuser 304 is made of ground glass whichspreads the emitted light with a Gausian intensity profile. In anotherembodiment the diffuser 304 includes glass beads. In some embodiments,the diffuser 304 is constructed so as to diffuse the emitted light in aLambertian pattern. A Lambertian pattern is one in which the radiationintensity is substantially constant throughout the area of dispersion.One such diffuser 304 is made from opal glass. Opal glass is similar toground glass, but has one surface coated with a milky white coating todiffuse light evenly. In an embodiment, the diffuser 304 is capable ofdistributing the emitted light on the surface of a plane (e.g., thesurface of the tissue measurement site 102) in a predefined geometry(e.g., a rectangle, square, or circle), and with a substantially uniformintensity profile and energy distribution. In some embodiments, theefficiency, or the amount of light transmitted by the diffuser 304, isgreater than 70% of the light emitted by the emitter 302. In someembodiments, the efficiency is greater than 90% of the emitted light.Other optical elements known in the art may be used for the diffuser304.

In an embodiment, the diffuser 304 has a substantially rectangular shapehaving dimensions within a range of approximately 0.5-2 cm in width andapproximately 1-4 centimeters in length. In another embodiment, thesubstantially rectangular shape of the diffuser 304 has dimensions ofapproximately 0.5 cm in width and approximately 1 cm in length. Inanother embodiment, the diffuser's 304 substantially rectangular shapehas dimensions of approximately 1 cm in width and approximately 1.5 cmin length. In yet another embodiment, the diffuser 304 has asubstantially square shape with dimensions in the range of approximately0.25-10 cm².

The light-absorbing detector filter 306, which is also depicted in FIG.4A in a top view, is a planar surface having an opening 402 throughwhich the emitted light may pass after being attenuated by the tissuemeasurement site 102. In the depicted embodiment, the opening 402 isrectangular-shaped, with dimensions substantially similar to theirradiated surface area 206. According to an embodiment, thelight-absorbing detector filter is substantially rectangular in shapeand has outer dimensions of 4 cm in width and 8 cm in length, and has anopening through which emitted light may pass, the opening havingdimensions of 2 cm in width and 5 cm in length. In another embodiment,the light-absorbing detector filter is substantially rectangular inshape and has outer dimensions in the range of 1-3 cm in width and 2-8cm in length, and has an opening through which emitted light may pass,the opening having dimensions in the range of 0.25-2 cm in width and 1-4cm in length. In yet another embodiment, the light-absorbing detectorfilter is substantially rectangular in shape and has outer dimensions of3 cm in width and 6 cm in length, and has an opening through whichemitted light may pass, the opening having dimensions of 1.5 cm in widthand 4 cm in length.

The top surface of the light-absorbing filter 306 (facing the tissuemeasurement site 102 and the emitter 302) is coated with a material thatabsorbs light, such as, for example, black pigment. Many other types oflight-absorbing materials are well known in the art and can be used withthe detector filter 306. During operation, light emitted from theemitter 302 can reflect off of the tissue measurement site 102 (or otherstructures within the 3D sensor 300) to neighboring portions of the 3Dsensor 300. If those neighboring portions of the 3D sensor 300 possessreflective surfaces, then the light can reflect back to the tissuemeasurement site 102, progress through the tissue and arrive at thedetector 310. Such multiple scattering can result in detecting photonswhose pathlengths are considerably longer than most of the light that isdetected, thereby introducing variations in pathlength which will affectthe accuracy of the measurements of the pulse oximetry 3D sensor 300.Advantageously, the light-absorbing filter 306 reduces or eliminates theamount of emitted light that is reflected in this manner because itabsorbs such reflected light, thereby stopping the chain of scatteringevents. In certain embodiments, the sensor-facing surfaces of otherportions of the 3D sensor 300 are covered in light-absorbing material tofurther decrease the effect of reflective multiple scattering.

The light concentrator 308 is a structure to receive the emitted opticalradiation, after attenuation by the tissue measurement site 102, tocollect and concentrate the dispersed optical radiation, and to directthe collected and concentrated optical radiation to the detector 310. Inan embodiment, the light concentrator 308 is made of ground glass orglass beads. In some embodiments, the light concentrator 308 includes acompound parabolic concentrator.

As described above with respect to FIG. 1, the detector 310 captures andmeasures light from the tissue measurement site 102. For example, thedetector 310 can capture and measure light transmitted from the emitter302 that has been attenuated by the tissue in the measurement site 102.The detector 310 can output a detector signal responsive to the lightcaptured or measured. The detector 310 can be implemented using one ormore photodiodes, phototransistors, or the like. In addition, aplurality of detectors 310 can be arranged in an array with a spatialconfiguration corresponding to the irradiated surface area 206 tocapture the attenuated or reflected light from the tissue measurementsite.

Referring to FIG. 4A, a top view of a portion of the 3D sensor 300 isprovided. The light-absorbing detector filter 306 is illustrated havinga top surface coated with a light-absorbing material. Thelight-absorbing material can be a black opaque material or coating orany other dark color or coating configured to absorb light.Additionally, a rectangular opening 402 is positioned relative to thelight concentrator 308 (shown in phantom) and the detector 310 such thatlight may pass through the rectangular opening 402, into the lightconcentrator 308, and to the detector 310. FIG. 4B illustrates the topview of a portion of the 3D sensor 300 as in FIG. 4A, with the additionof the tissue measurement site 102 in operational position. Accordingly,the rectangular opening 402, the light concentrator 308 and the detector310 are shown in phantom as being under the tissue measurement site 102.In FIGS. 4A and 4B, the light concentrator 308 is shown to havedimensions significantly larger than the dimensions of the rectangularopening 402. In other embodiments, the dimensions of the lightconcentrator 308, the rectangular opening 402, and the irradiatedsurface area 206 are substantially similar.

FIG. 5 illustrates a top view of a 3D pulse oximetry sensor 500according to an embodiment of the present disclosure. The 3D sensor 500is configured to be worn on a patient's finger 102. The 3D sensor 500includes an adhesive substrate 502 having front flaps 504 and rear flaps506 extending outward from a center portion 508 of the 3D sensor 500.The center portion 508 includes components of the 3D pulse oximetrysensor 300 described with respect to FIGS. 3, 4A and 4B. On the frontside of the adhesive substrate 502 the emitter 302 and the lightdiffuser 304 are positioned. On the rear side of the adhesive substrate502 the light-absorbent detector filter 306, the light concentrator 308and the detector 310 are positioned. In use, the patient's fingerserving as the tissue measurement site 102 is positioned over therectangular opening 402 such that when the front portion of the adhesivesubstrate is folded over on top of the patient's finger 102, the emitter302 and the light diffuser 304 are aligned with the measurement site102, the filter 306, the light concentrator 308 and the detector 310.Once alignment is established, the front and rear flaps 504, 506 can bewrapped around the finger measurement site 102 such that the adhesivesubstrate 502 provides a secure contact between the patient's skin andthe 3D sensor 500. FIG. 5 also illustrates an example of a sensorconnector cable 510 which is used to connect the 3D sensor 500 to amonitor 809, as described with respect to FIG. 8.

FIG. 6 is a simplified schematic illustration of a conventional, 2Dapproach to reflective pulse oximetry in which the emitter is configuredto emit optical radiation as a point optical source. Reflective pulseoximetry is a method by which the emitter and detector are located onthe same side of the tissue measurement site 102. Light is emitted intoa tissue measurement site 102 and attenuated. The emitted light passesinto the tissue 102 and is then reflected back to the same side of thetissue measurement site 102 as the emitter. As illustrated in FIG. 6, adepicted reflective 2D pulse oximetry sensor 600 includes an emitter602, a light block 606, and a detector 610. The light block 606 isnecessary because the emitter 602 and the detector 610 are located onthe same side of the tissue measurement site 102. Accordingly, the lightblock 606 prevents incident emitter light, which did not enter thetissue measurement site 102, from arriving at the detector 610. Thedepicted 2D pulse oximetry sensor 600 is configured to emit light as apoint source. As depicted in FIG. 6, a simplified illustration of thelight path 620 of the emitted light from the emitter 602, through thetissue measurement site 102, and to the detector 610 is provided.Notably, a point source of light is emitted, and a point source of lightis detected. As discussed above with respect to FIG. 1, use of a pointoptical source can result in substantial measurement error due topathlength variability resulting from the multiple scatter phenomenon.The sample space provided by a 2D point optical emitter source is notlarge enough to account for pathlength variability, which will skewmeasurement results.

FIGS. 7A and 7B are simplified schematic side and top views,respectively, of a 3D reflective pulse oximetry sensor 700 according toan embodiment of the present disclosure. In the illustrated embodiment,the 3D sensor 700 irradiates the tissue measurement site 102 and detectsthe emitted light that is reflected by the tissue measurement site 102.The 3D sensor 700 can be placed on a portion of the patient's body thathas relatively flat surface, such as, for example a wrist, because theemitter 702 and detector 710 are on located the same side of the tissuemeasurement site 102. The 3D sensor 700 includes an emitter 702, a lightdiffuser 704, a light block 706, a light concentrator 708, and adetector 710.

As previously described, the emitter 702 can serve as the source ofoptical radiation transmitted towards the tissue measurement site 102.The emitter 702 can include one or more sources of optical radiation.Such sources of optical radiation can include LEDs, laser diodes,incandescent bulbs with appropriate frequency-selective filters,combinations of the same, or the like. In an embodiment, the emitter 702includes sets of optical sources that are capable of emitting visibleand near-infrared optical radiation. In some embodiments, the emitter702 transmits optical radiation of red and infrared wavelengths, atapproximately 650 nm and approximately 940 nm, respectively. In someembodiments, the emitter 702 includes a single source of opticalradiation.

The light diffuser 704 receives the optical radiation emitted from theemitter 302 and homogenously spreads the optical radiation over a wide,donut-shaped area, such as the area outlined by the light diffuser 704as depicted in FIG. 7B. Advantageously, the diffuser 704 can receiveemitted light in the form of a 2D point optical source (or any otherform) and spread the light to fit the desired surface area on a planedefined by the surface of the tissue measurement site 102. In anembodiment, the diffuser 704 is made of ground glass or glass beads. Askilled artisan will understand that may other materials can be used tomake the light diffuser 704.

The light blocker 706 includes an annular ring having a cover portion707 sized and shaped to form a light isolation chamber for the lightconcentrator 708 and the detector 710. (For purposes of illustration,the light block cover 707 is not illustrated in FIG. 7B.) The lightblocker 706 and the cover 707 can be made of any material that opticallyisolates the light concentrator 708 and the detector 710. The lightisolation chamber formed by the light blocker 706 and cover 708 ensuresthat the only light detected by the detector 710 is light that isreflected from the tissue measurement site.

The light concentrator 708 is a cylindrical structure with a truncatedcircular conical structure on top, the truncated section of which ofwhich is adjacent the detector 710. The light concentrator 708 isstructured to receive the emitted optical radiation, after reflection bythe tissue measurement site 102, and to direct the reflected light tothe detector 710. In an embodiment, the light concentrator 708 is madeof ground glass or glass beads. In some embodiments, the lightconcentrator 708 includes a compound parabolic concentrator.

As previously described, the detector 710 captures and measures lightfrom the tissue measurement site 102. For example, the detector 710 cancapture and measure light transmitted from the emitter 702 that has beenreflected from the tissue in the measurement site 102. The detector 710can output a detector signal responsive to the light captured ormeasured. The detector 710 can be implemented using one or morephotodiodes, phototransistors, or the like. In addition, a plurality ofdetectors 710 can be arranged in an array with a spatial configurationcorresponding to the irradiated surface area depicted in FIG. 7B by thelight concentrator 708 to capture the reflected light from the tissuemeasurement site.

Advantageously, the light path 720 illustrated in FIG. 7A depicts asubstantial sample of reflected light that enter the light isolationchamber formed by the light blocker 706 and cover 707. As previouslydiscussed, the large sample of reflected light (as compared to thereflected light collected using the 2D point optical source approach)provides the opportunity to take an average of the detected light, toderive a more accurate measurement of the emitted light absorbed by thetissue, which will lead to a more accurate oxygen saturationmeasurement.

Referring now to FIG. 7B, a top view of the 3D sensor 700 is illustratedwith both the emitter 702 and the light blocker cover 707 removed forease of illustration. The outer ring illustrates the footprint of thelight diffuser 704. As light is emitted from the emitter 702 (not shownin FIG. 7B), it is diffused homogenously and directed to the tissuemeasurement site 102. The light blocker 706 forms the circular wall of alight isolation chamber to keep incident light from being sensed by thedetector 710. The light blocker cover 707 blocks incidental light fromentering the light isolation chamber from above. The light concentrator708 collects the reflected light from the tissue measurement site 102and funnels it upward toward the detector 710 at the center of the 3Dsensor 700.

FIG. 8 illustrates an example of an optical physiological measurementsystem 800, which may also be referred to herein as a pulse oximetrysystem 800. In certain embodiments, the pulse oximetry system 800noninvasively measures a blood analyte, such as oxygen,carboxyhemoglobin, methemoglobin, total hemoglobin, glucose, proteins,lipids, a percentage thereof (e.g., saturation), pulse rate, perfusionindex, oxygen content, total hemoglobin, Oxygen Reserve Index™ (ORI™) ormany other physiologically relevant patient characteristics. Thesecharacteristics can relate to, for example, pulse rate, hydration,trending information and analysis, and the like. The system 800 can alsomeasure additional blood analytes and/or other physiological parametersuseful in determining a state or trend of wellness of a patient.

The pulse oximetry system 800 can measure analyte concentrations atleast in part by detecting optical radiation attenuated by tissue at ameasurement site 102. The measurement site 102 can be any location on apatient's body, such as a finger, foot, earlobe, wrist, forehead, or thelike.

The pulse oximetry system 800 can include a sensor 801 (or multiplesensors) that is coupled to a processing device or physiological monitor809. In an embodiment, the sensor 801 and the monitor 809 are integratedtogether into a single unit. In another embodiment, the sensor 801 andthe monitor 809 are separate from each other and communicate with oneanother in any suitable manner, such as via a wired or wirelessconnection. The sensor 801 and monitor 809 can be attachable anddetachable from each other for the convenience of the user or caregiver,for ease of storage, sterility issues, or the like.

In the depicted embodiment shown in FIG. 8, the sensor 801 includes anemitter 804, a detector 806, and a front-end interface 808. The emitter804 can serve as the source of optical radiation transmitted towardsmeasurement site 102. The emitter 804 can include one or more sources ofoptical radiation, such as light emitting diodes (LEDs), laser diodes,incandescent bulbs with appropriate frequency-selective filters,combinations of the same, or the like. In an embodiment, the emitter 804includes sets of optical sources that are capable of emitting visibleand near-infrared optical radiation.

The pulse oximetry system 800 also includes a driver 811 that drives theemitter 804. The driver 111 can be a circuit or the like that iscontrolled by the monitor 809. For example, the driver 811 can providepulses of current to the emitter 804. In an embodiment, the driver 811drives the emitter 804 in a progressive fashion, such as in analternating manner. The driver 811 can drive the emitter 804 with aseries of pulses for some wavelengths that can penetrate tissuerelatively well and for other wavelengths that tend to be significantlyabsorbed in tissue. A wide variety of other driving powers and drivingmethodologies can be used in various embodiments. The driver 811 can besynchronized with other parts of the sensor 801 to minimize or reducejitter in the timing of pulses of optical radiation emitted from theemitter 804. In some embodiments, the driver 811 is capable of drivingthe emitter 804 to emit optical radiation in a pattern that varies byless than about 10 parts-per-million.

The detector 806 captures and measures light from the tissue measurementsite 102. For example, the detector 806 can capture and measure lighttransmitted from the emitter 804 that has been attenuated or reflectedfrom the tissue at the measurement site 102. The detector 806 can outputa detector signal 107 responsive to the light captured and measured. Thedetector 806 can be implemented using one or more photodiodes,phototransistors, or the like. In some embodiments, a detector 806 isimplemented in detector package to capture and measure light from thetissue measurement site 102 of the patient. The detector package caninclude a photodiode chip mounted to leads and enclosed in anencapsulant. In some embodiments, the dimensions of the detector packageare approximately 2 square centimeters. In other embodiments, thedimensions of the detector package are approximately 1.5 centimeters inwidth and approximately 2 centimeters in length.

The front-end interface 808 provides an interface that adapts the outputof the detectors 806, which is responsive to desired physiologicalparameters. For example, the front-end interface 808 can adapt thesignal 807 received from the detector 806 into a form that can beprocessed by the monitor 809, for example, by a signal processor 810 inthe monitor 809. The front-end interface 808 can have its componentsassembled in the sensor 801, in the monitor 809, in a connecting cabling(if used), in combinations of the same, or the like. The location of thefront-end interface 808 can be chosen based on various factors includingspace desired for components, desired noise reductions or limits,desired heat reductions or limits, and the like.

The front-end interface 808 can be coupled to the detector 806 and tothe signal processor 810 using a bus, wire, electrical or optical cable,flex circuit, or some other form of signal connection. The front-endinterface 808 can also be at least partially integrated with variouscomponents, such as the detectors 806. For example, the front-endinterface 808 can include one or more integrated circuits that are onthe same circuit board as the detector 806. Other configurations canalso be used.

As shown in FIG. 8, the monitor 909 can include the signal processor 810and a user interface, such as a display 812. The monitor 809 can alsoinclude optional outputs alone or in combination with the display 812,such as a storage device 814 and a network interface 816. In anembodiment, the signal processor 810 includes processing logic thatdetermines measurements for desired analytes based on the signalsreceived from the detector 806. The signal processor 810 can beimplemented using one or more microprocessors or sub-processors (e.g.,cores), digital signal processors, application specific integratedcircuits (ASICs), field programmable gate arrays (FPGAs), combinationsof the same, and the like.

The signal processor 810 can provide various signals that control theoperation of the sensor 801. For example, the signal processor 810 canprovide an emitter control signal to the driver 811. This control signalcan be useful in order to synchronize, minimize, or reduce jitter in thetiming of pulses emitted from the emitter 804. Accordingly, this controlsignal can be useful in order to cause optical radiation pulses emittedfrom the emitter 804 to follow a precise timing and consistent pattern.For example, when a transimpedance-based front-end interface 808 isused, the control signal from the signal processor 810 can providesynchronization with an analog-to-digital converter (ADC) in order toavoid aliasing, cross-talk, and the like. As also shown, an optionalmemory 813 can be included in the front-end interface 808 and/or in thesignal processor 810. This memory 813 can serve as a buffer or storagelocation for the front-end interface 808 and/or the signal processor810, among other uses.

The user interface 812 can provide an output, e.g., on a display, forpresentation to a user of the pulse oximetry system 800. The userinterface 812 can be implemented as a touch-screen display, a liquidcrystal display (LCD), an organic LED display, or the like. Inalternative embodiments, the pulse oximetry system 800 can be providedwithout a user interface 812 and can simply provide an output signal toa separate display or system.

The storage device 814 and a network interface 816 represent otheroptional output connections that can be included in the monitor 809. Thestorage device 814 can include any computer-readable medium, such as amemory device, hard disk storage, EEPROM, flash drive, or the like. Thevarious software and/or firmware applications can be stored in thestorage device 814, which can be executed by the signal processor 810 oranother processor of the monitor 809. The network interface 816 can be aserial bus port (RS-232/RS-485), a Universal Serial Bus (USB) port, anEthernet port, a wireless interface (e.g., WiFi such as any 802.1xinterface, including an internal wireless card), or other suitablecommunication device(s) that allows the monitor 809 to communicate andshare data with other devices. The monitor 809 can also include variousother components not shown, such as a microprocessor, graphicsprocessor, or controller to output the user interface 812, to controldata communications, to compute data trending, or to perform otheroperations.

Although not shown in the depicted embodiment, the pulse oximetry system800 can include various other components or can be configured indifferent ways. For example, the sensor 801 can have both the emitter804 and detector 806 on the same side of the tissue measurement site 102and use reflectance to measure analytes.

Although the foregoing disclosure has been described in terms of certainpreferred embodiments, many other variations than those described hereinwill be apparent to those of ordinary skill in the art.

Conditional language used herein, such as, among others, “can,” “might,”“may,” “e.g.,” and the like, unless specifically stated otherwise, orotherwise understood within the context as used, is generally intendedto convey that certain embodiments include, while other embodiments donot include, certain features, elements and/or states. Thus, suchconditional language is not generally intended to imply that features,elements and/or states are in any way required for one or moreembodiments or that one or more embodiments necessarily include logicfor deciding, with or without author input or prompting, whether thesefeatures, elements and/or states are included or are to be performed inany particular embodiment. The terms “comprising,” “including,”“having,” and the like are synonymous and are used inclusively, in anopen-ended fashion, and do not exclude additional elements, features,acts, operations, and so forth. Also, the term “or” is used in itsinclusive sense (and not in its exclusive sense) so that when used, forexample, to connect a list of elements, the term “or” means one, some,or all of the elements in the list. Further, the term “each,” as usedherein, in addition to having its ordinary meaning, can mean any subsetof a set of elements to which the term “each” is applied.

While the above detailed description has shown, described, and pointedout novel features as applied to various embodiments, it will beunderstood that various omissions, substitutions, and changes in theform and details of the systems, devices or algorithms illustrated canbe made without departing from the spirit of the disclosure. As will berecognized, certain embodiments of the disclosure described herein canbe embodied within a form that does not provide all of the features andbenefits set forth herein, as some features can be used or practicedseparately from others.

The term “and/or” herein has its broadest, least limiting meaning whichis the disclosure includes A alone, B alone, both A and B together, or Aor B alternatively, but does not require both A and B or require one ofA or one of B. As used herein, the phrase “at least one of” A, B, “and”C should be construed to mean a logical A or B or C, using anon-exclusive logical or.

The apparatuses and methods described herein may be implemented by oneor more computer programs executed by one or more processors. Thecomputer programs include processor-executable instructions that arestored on a non-transitory tangible computer readable medium. Thecomputer programs may also include stored data. Non-limiting examples ofthe non-transitory tangible computer readable medium are nonvolatilememory, magnetic storage, and optical storage. Although the foregoingdisclosure has been described in terms of certain preferred embodiments,other embodiments will be apparent to those of ordinary skill in the artfrom the disclosure herein. Additionally, other combinations, omissions,substitutions and modifications will be apparent to the skilled artisanin view of the disclosure herein. Accordingly, the present invention isnot intended to be limited by the description of the preferredembodiments, but is to be defined by reference to claims.

Additionally, all publications, patents, and patent applicationsmentioned in this specification are herein incorporated by reference tothe same extent as if each individual publication, patent, or patentapplication were specifically and individually indicated to beincorporated by reference.

What is claimed is:
 1. An optical physiological measurement deviceconfigured for placement on a patient at a tissue measurement site, thedevice comprising: one or more emitters configured to emit light so asto irradiate the tissue measurement site; and a plurality of detectorsconfigured to detect the emitted light after attenuation by andreflection from a portion of the tissue measurement site, the portion ofthe tissue measurement site having an at least partially circular shapebounded by a light block, the tissue measurement site located on a wristof the patient, the plurality of detectors further configured totransmit a signal responsive to the detected light; wherein the lightblock comprises an annular ring having a circular shape located betweenthe emitted light at the tissue measurement site and the plurality ofdetectors, the light block reducing an amount of incident light emittedfrom the one or more emitters from being detected by the plurality ofdetectors, wherein the plurality of detectors are arranged in an arrayhaving a spatial configuration corresponding to the shape of the portionof the tissue measurement site.
 2. The optical physiological measurementdevice of claim 1, further comprising a processor configured to receivethe transmitted signal responsive to the detected light and to determinea physiological parameter.
 3. The optical physiological measurementdevice of claim 2, wherein the parameter is arterial oxygen saturation.4. The optical physiological measurement device of claim 1, furthercomprising a diffuser which receives, spreads and emits the spreadlight, wherein the emitted spread light is directed at the tissuemeasurement site.
 5. The optical physiological measurement device ofclaim 4, further comprising a concentrator which receives the lightafter attenuation by tissue of the patient, concentrates the receivedlight and emits the concentrated light in the direction of the pluralityof detectors.
 6. The optical physiological measurement device of claim5, wherein the concentrator comprises at least one of glass, groundglass, glass beads, opal glass, and a compound parabolic concentrator.7. The optical physiological measurement device of claim 4, wherein thediffuser comprises at least one of a glass diffuser, ground glassdiffuser, a glass bead diffuser, an opal glass diffuser, and anengineered diffuser.
 8. The optical physiological measurement device ofclaim 4, wherein the diffuser emits the spread light with asubstantially uniform intensity profile.
 9. The optical physiologicalmeasurement system of claim 4, wherein the diffuser defines a surfacearea shape by which the emitted spread light is distributed onto asurface of the tissue measurement site.
 10. The optical physiologicalmeasurement device of claim 1, wherein the one or more emitters arepositioned outside the annular ring when the optical physiologicalmeasurement device is placed on the patient at the tissue measurementsite, and wherein the plurality of detectors are positioned inside theannular ring when the optical physiological measurement device is placedon the patient at the tissue measurement site.
 11. A method to determinea constituent or analyte in a patient's blood, the method comprising:emitting, from at least one emitter of an optical sensor, light of oneor more wavelengths so as to irradiate a tissue measurement site,wherein the tissue measurement site is located on a wrist of a patient;detecting, with a plurality of detectors, the emitted light afterattenuation by and reflection from a portion of the tissue measurementsite, the portion having an at least partially circular shape; andproviding an annular ring located between the emitted light at thetissue measurement site and the plurality of detectors, wherein theannular ring reduces an amount of incident light emitted from the atleast one emitter from arriving at the plurality of detectors, andwherein the plurality of detectors are arranged in an array having aspatial configuration corresponding to the shape of the portion of thetissue measurement site.
 12. The method of claim 11, further comprising:transmitting, from the a plurality of detectors, a signal responsive tothe detected light; receiving, by a processor, the transmitted signalresponsive to the detected light; and processing, by the processor, thereceived signal responsive to the detected light to determine aphysiological parameter.
 13. The method of claim 11, further comprisingspreading, with a diffuser, the emitted light and emitting the spreadlight from the diffuser to the tissue measurement site, wherein thediffuser spreads the light over a greater area of the tissue measurementsite than would otherwise be illuminated by the emitter directlyemitting light at the tissue measurement site.
 14. The method of claim13, further comprising receiving, by a concentrator, the emitted spreadlight after the spread light has been attenuated by and reflected fromthe tissue measurement site and concentrating, by the concentrator, thereceived light and emitting the concentrated light from the concentratorto the a plurality of detectors.
 15. The method of claim 14, whereinconcentrating, by the concentrator, the received light and emitting theconcentrated light from the concentrator to the plurality of detectorsis performed by at least one of a glass concentrator, a glass beadconcentrator, an opal glass concentrator, and a compound parabolicconcentrator.
 16. The method of claim 13, wherein spreading, with adiffuser, the emitted light and emitting the spread light from thediffuser to the tissue measurement site is performed by at least one ofa glass diffuser, a glass bead diffuser, an opal glass diffuser, and anengineered diffuser.
 17. The method of claim 13, wherein spreading, witha diffuser, the emitted light and emitting the spread light from thediffuser to the tissue measurement site further comprises spreading theemitted light with a substantially uniform intensity profile.
 18. Themethod of claim 13, wherein spreading, with a diffuser, the emittedlight and emitting the spread light from the diffuser to the tissuemeasurement site further comprises spreading the emitted light so as todefine a surface area shape by which the emitted spread light isdistributed onto a surface of the tissue measurement site.
 19. Themethod of claim 11, wherein the at least one emitter is positionedoutside the annular ring when the optical sensor is placed on thepatient at the tissue measurement site, and wherein the plurality ofdetectors are positioned inside the annular ring when the optical sensoris placed on the patient at the tissue measurement site.
 20. A pulseoximeter sensor comprising: one or more optical sources configured toemit light at one or more wavelengths, wherein, when the pulse oximetersensor is placed on a patient at a tissue measurement site, the one ormore optical sources are positioned in a reflectance measurementconfiguration on a first side of the tissue measurement site, andwherein the one or more optical sources are configured to irradiate thetissue measurement site; a plurality of detectors configured to detectlight emitted from the one or more optical sources after attenuation bya portion of the tissue measurement site, the portion of the tissuemeasurement site having an at least partially circular shape, theplurality of detectors arranged in an array having a spatialconfiguration corresponding to the shape of the portion of the tissuemeasurement site so as to capture the emitted light reflected from thetissue measurement site, wherein the plurality of detectors arepositioned in a reflectance measurement configuration on the first sideof the tissue measurement site when the pulse oximeter sensor is placedon the patient, the plurality of detectors further configured to outputa signal responsive to the detected light; and a light block comprisingan annular ring located between the emitted light at the tissuemeasurement site and the plurality of detectors, the light blockreducing an amount of incident light emitted from the one or moreoptical sources from arriving at the plurality of detectors.
 21. Thepulse oximeter sensor of claim 20, further comprising a concentratorwhich concentrates the emitted light after it has been attenuated by thetissue measurement site and directs the concentrated light toward theplurality of detectors.
 22. The pulse oximeter sensor of claim 20,wherein the plurality of detectors are further configured to output thesignals response to the detected light to a processor configured toreceive the signals responsive to the detected light and to determine aphysiological parameter.
 23. The pulse oximeter sensor of claim 20,further comprising a diffuser configured to receive the emitted light,to spread the received light, and to emit the spread light, wherein theemitted spread light is directed at the tissue measurement site.
 24. Thepulse oximeter sensor of claim 23, wherein the diffuser is furtherconfigured to define a surface area shape by which the emitted spreadlight is distributed onto a surface of the tissue measurement site. 25.The pulse oximeter sensor of claim 20, wherein the one or more opticalsources are positioned outside the annular ring when the pulse oximetersensor is placed on the patient at the tissue measurement site, andwherein the plurality of detectors are positioned inside the annularring when the pulse oximeter sensor is placed on the patient at thetissue measurement site.
 26. A pulse oximeter sensor comprising: one ormore optical sources configured to emit light at one or morewavelengths, wherein, when the pulse oximeter sensor is placed on apatient at a tissue measurement site, the one or more optical sourcesare positioned in a reflectance measurement configuration on a firstside of the tissue measurement site, and wherein the one or more opticalsources are configured to irradiate the tissue measurement site, andwherein the tissue measurement site is located on a wrist of thepatient; a plurality of detectors configured to detect light emittedfrom the one or more optical sources after attenuation by and reflectionfrom a portion of the tissue measurement site, the portion of the tissuemeasurement site having an annular shape, wherein the plurality ofdetectors are positioned in a reflectance measurement configuration onthe first side of the tissue measurement site when the pulse oximetersensor is placed on the patient, the plurality of detectors furtherconfigured to output signals responsive to the detected light; and alight block comprising an annular ring located between the emitted lightat the tissue measurement site and the plurality of detectors, the lightblock reducing an amount of incident light emitted from the one or moreoptical sources that does not enter the tissue measurement site arrivingat the plurality of detectors, wherein the plurality of detectors arepositioned in an array having a spatial configuration corresponding tothe annular shape of the portion of the tissue measurement site.
 27. Thepulse oximeter sensor of claim 26, wherein the plurality of detectorsare further configured to transmit the output signals responsive to thedetected light to a processor configured to receive the signalsresponsive to the detected light and to determine a physiologicalparameter.
 28. The pulse oximeter sensor of claim 26, wherein the one ormore optical sources are positioned outside the annular ring when thepulse oximeter sensor is placed on the patient at the tissue measurementsite, and wherein the plurality of detectors are positioned inside theannular ring when the pulse oximeter sensor is placed on the patient atthe tissue measurement site.